928 research outputs found
OFF-FARM INCOME, TECHNOLOGY ADOPTION, AND FARM ECONOMIC PERFORMANCE
The economic well-being of most U.S. farm households depends on income from both onfarm and off-farm activities. Consequently, for many farm households, economic decisions (including technology adoption and other production decisions) are likely to be shaped by the allocation of managerial time among such activities. While time allocation decisions are usually not measured directly, we observe the outcomes of such decisions, such as onfarm and off-farm income. This report finds that a farm operator’s off-farm employment and off-farm income vary inversely with the size of the farm. Operators of smaller farm operations improve their economic performance by compensating for the scale disadvantages of their farm business with more off-farm involvement. Off-farm work reduces farm-level technical efficiency, but increases household-level technical efficiency. And adoption of agricultural innovations that save managerial time is associated with higher off-farm income.Off-farm income, farm households, economic performance, managerial time, scale economies, scope economies, technical efficiency, technology adoption, farm size, Agricultural Finance, Farm Management,
The North American toxic fungal pathogen G3 Claviceps purpurea (Fries) Tulasne is established in the German Wadden Sea.
Three lineages (G1, G2 and G3) within the toxic invasive ergot fungus Claviceps purpurea (Fries) Tulasne are known; these should be recognized as unique species, or at least as varieties. On 2 November 2011, a very dense, well established population of G3 C. purpurea was found on the common cord-grass Spartina anglica C.E. Hubbard at two localities on the German North Sea coast in the Wadden Sea (Caciliengroden and Hooksiel). It is most likely that G3 C. purpurea has a North American origin and entered German coastal waters by floating sclerotia from Irish, British, or Benelux waters, where it was previously found. However, introduction via ships’ ballast water coming from their native or introduced ranges is also plausible. Furthermore imports of G3 sclerotia via seed mussels collected from wild subtidal banks in Irish, British and Dutch coastal waters and released into the German Wadden Sea can currently not be excluded. Risks from this highly toxic fungus for human, grazing animals and the marine environment have been identified but not yet quantified in terms of impact. A suitable monitoring programme should be implemented to detect any unwanted impacts caused by G3 C. purpurea in German salt marshes at an early phase
External and intrinsic anchoring in nematic liquid crystals: A Monte Carlo study
We present a Monte Carlo study of external surface anchoring in nematic cells
with partially disordered solid substrates, as well as of intrinsic anchoring
at free nematic interfaces. The simulations are based on the simple hexagonal
lattice model with a spatially anisotropic intermolecular potential. We
estimate the corresponding extrapolation length by imposing an elastic
deformation in a hybrid cell-like nematic sample. Our estimates for
increase with increasing surface disorder and are essentially
temperature--independent. Experimental values of are approached only when
both the coupling of nematic molecules with the substrate and the anisotropy of
nematic--nematic interactions are weak.Comment: Revisions primarily in section I
Sequential Deliberation for Social Choice
In large scale collective decision making, social choice is a normative study
of how one ought to design a protocol for reaching consensus. However, in
instances where the underlying decision space is too large or complex for
ordinal voting, standard voting methods of social choice may be impractical.
How then can we design a mechanism - preferably decentralized, simple,
scalable, and not requiring any special knowledge of the decision space - to
reach consensus? We propose sequential deliberation as a natural solution to
this problem. In this iterative method, successive pairs of agents bargain over
the decision space using the previous decision as a disagreement alternative.
We describe the general method and analyze the quality of its outcome when the
space of preferences define a median graph. We show that sequential
deliberation finds a 1.208- approximation to the optimal social cost on such
graphs, coming very close to this value with only a small constant number of
agents sampled from the population. We also show lower bounds on simpler
classes of mechanisms to justify our design choices. We further show that
sequential deliberation is ex-post Pareto efficient and has truthful reporting
as an equilibrium of the induced extensive form game. We finally show that for
general metric spaces, the second moment of of the distribution of social cost
of the outcomes produced by sequential deliberation is also bounded
Newly observed two-body decays of B mesons in a hybrid perspective
In consistency with the b --> c type of (quasi) two body decays, recently
observed two body decays of B mesons are studied in a hybrid perspective in
which their amplitude is given by a sum of factorizable and non-factorizable
ones, and a role of the latter in these decays are discussed.Comment: 7 page
Reconstructing the relatedness of cooperatively breeding queens in the Panamanian leaf-cutting ant Acromyrmex echinatior (Hymenoptera: Formicidae)
The evolution of permanent inquiline social parasites in ants has been conjectured to be facilitated by secondary poly gyny, that is, the re-adoption of new queens into existing mature colonies. This idea was first formulated by Wasmann, Wheeler, and Emery more than a century ago. Emery predicted that inquilines should be the sister-lineages of their hosts, which prompted Alfred Buschinger to propose that they evolve by sympatric speciation. However, these scenarios hinge on two vital conditions that have not been quantitatively documented: 1. That host sister species are secondarily polygynous and primarily recruit close kin, and 2. That such adoptions are prone to occasional mistakes that would select for the condition-dependent expression of exploitative traits and reproductive isolation by disruptive selection. Here, we use a long-term data set on the leaf-cutting ant Acromyrmex echinatior (ForEl, 1899), known to have a closely related inquiline social parasite A. insinuator schultz, BEKKEvolD & Boomsma, 1998, to address the first of these conditions. We estimate the frequency of secondary polygyny and the degree to which cooperatively breeding queens are related. We find that the overall frequency of polygynous colonies is ca. 8% and that polygynous colonies typically have two queens. Most queen pairs are first-degree relatives, consistent with colonies adopting one or two daughters either before or just after becoming orphaned. However, we also document a few pairs of cooperatively breeding queens that are unrelated and estimate that this social structure may apply to ca. 20% of the polygynous colonies, and thus ca. 1% of all colonies. Our findings show that the breeding system of A. echinatior matches the polygyny characteristics that are believed to facilitate the emergence of socially parasitic queen morphs
Topological Defects and Interactions in Nematic Emulsions
Inverse nematic emulsions in which surfactant-coated water droplets are
dispersed in a nematic host fluid have distinctive properties that set them
apart from dispersions of two isotropic fluids or of nematic droplets in an
isotropic fluid. We present a comprehensive theoretical study of the
distortions produced in the nematic host by the dispersed droplets and of
solvent mediated dipolar interactions between droplets that lead to their
experimentally observed chaining. A single droplet in a nematic host acts like
a macroscopic hedgehog defect. Global boundary conditions force the nucleation
of compensating topological defects in the nematic host. Using variational
techniques, we show that in the lowest energy configuration, a single water
droplet draws a single hedgehog out of the nematic host to form a tightly bound
dipole. Configurations in which the water droplet is encircled by a
disclination ring have higher energy. The droplet-dipole induces distortions in
the nematic host that lead to an effective dipole-dipole interaction between
droplets and hence to chaining.Comment: 17 double column pages prepared by RevTex, 15 eps figures included in
text, 2 gif figures for Fig. 1
Sequential two-player games with ambiguity
Author's pre-printIf players' beliefs are strictly nonadditive, the Dempster–Shafer updating rule can be used to define beliefs off the equilibrium path. We define an equilibrium concept in sequential two-person games where players update their beliefs with the Dempster–Shafer updating rule. We show that in the limit as uncertainty tends to zero, our equilibrium approximates Bayesian Nash equilibrium. We argue that our equilibrium can be used to define a refinement of Bayesian Nash equilibrium by imposing context-dependent constraints on beliefs under uncertainty.ESRC senior research fellowship scheme, H5242750259
New FOCUS results on charm mixing and CP violation
We present a summary of recent results on CP violation and mixing in the
charm quark sector based on a high statistics sample collected by
photoproduction experiment FOCUS (E831 at Fermilab). We have measured the
difference in lifetimes for the decays: and . This translates into a measurement of the mixing parameter in
the \d0d0 system, under the assumptions that is an equal mixture of
CP odd and CP even eigenstates, and CP violation is negligible in the neutral
charm meson system. We verified the latter assumption by searching for a CP
violating asymmetry in the Cabibbo suppressed decay modes , and . We show preliminary
results on a measurement of the branching ratio .Comment: 9 pages, 6 figures, requires espcrc2.sty. Presented by S.Bianco at
CPConf2000, September 2000, Ferrara (Italy). In this revision, fixed several
stylistic flaws, add two significant references, fixed a typo in Tab.
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